Question

Look at the digits 36, 42, 54, 28, 84 and 77Write down all the numbers which have 7 as a factor:

Answer 1

Express the given digits as a prime factorization.

$36=2\times2\times3\times3$

It can be observed that the factor of 36 does not have a factor of 7.

Similarly,

$\begin{gathered} 42=2\times3\times7 \\ 54=2\times3\times3\times3 \\ 28=2\times2\times7 \\ 84=2\times2\times3\times7 \\ 77=7\times11 \end{gathered}$

Observe that 42, 28, 84, and 77 have a factor of 7.